Generally, a photovoltaic cell converts the energy of light emitted from the sun into electricity. The elementary unit for generating the electric power through photoelectric effects is called a cell, and a plurality of cells for generating the electric power through serial or parallel connection with each other is called a photovoltaic module. A photovoltaic plant (which is called ‘photovoltaic system’) is an assembly of structures each having the plurality of photovoltaic modules connected in serial or parallel relation with each other.
The photovoltaic system is generally disposed on the land, which needs high land purchase and civil engineering work costs, and further, the land for the photovoltaic system is formed by flattening low mountains, which causes surrounding environments to be undesirably destroyed. Moreover, the photovoltaic modules are heated by the heat generated from the land in summer seasons so that they are not effectively cooled, thereby lowering their power generation efficiency.
So as to solve the above-mentioned problems, there are proposed methods for installing the photovoltaic system on water such as lake, river, pond, dam and the like. Such floating photovoltaic system makes use of a plurality of floating structures disposed on the surface of water together with buoys, the floating structures having a plurality of photovoltaic modules arranged thereon. In the state wherein the floating structures for the floating photovoltaic system are floating on the surface of water, they do not have to be displaced over a set range from their installed position through the stream of water or external forces like wind, and further, they do not have to have any rotations like pitch, roll and yaw. If they are displaced on the surface of water or if they have the rotations like pitch, roll and yaw, the sun and the photovoltaic modules may be misaligned with respect to each other to lower the amount of power generated from the floating photovoltaic system, and otherwise, the photovoltaic modules may be broken by the collision with objects.
FIG. 1 is photographs showing conventional floating photovoltaic systems.
Referring first to FIG. 1a, the conventional floating photovoltaic system is configured wherein front row structures and rear row structures are fixedly connected with each other by means of structure members, without any movements, and paths for a worker are formed between the front row structures and the rear row structures to conduct the maintenance of the floating photovoltaic system. In case of the conventional floating photovoltaic system as shown in FIG. 1a, however, the whole weight of the system become large, thereby increasing the construction cost thereof, and if the irregular bottom surface of a reservoir is exposed to the outside by drought, the conventional floating photovoltaic system may be broken due to its local load. In this configuration of the conventional floating photovoltaic system, ropes are connected to the outside portions of the wholly connected structures and tied up to anchors fixed to the bottom of the reservoir.
Other conventional floating photovoltaic systems are shown in FIGS. 1b and 1c, which are improvements of the conventional floating photovoltaic system of FIG. 1a. Referring now to FIGS. 1b and 1c, the conventional floating photovoltaic systems are configured wherein paths for a worker are formed between front and rear row structures on which photovoltaic modules are mounted so that the front row structures and the rear row structures are connected with each other in a hinge connection way at a height corresponding to the surface of water. In case of the conventional floating photovoltaic systems as shown in FIGS. 1b and 1c, if the irregular bottom surface of a reservoir is exposed to the outside by drought, the conventional floating photovoltaic systems may be not broken well due to their local load, but if wind blows, they may have rotations like pitch, roll and yaw. When the worker moves along the paths, further, he or she is likely to lose his or her balance on the paths, thereby making it hard to conduct the maintenance of the systems.
The reason why the conventional floating photovoltaic systems as shown in FIGS. 1b and 1c are weak to the rotations like pitch, roll and yaw is that the front row structures and the rear row structures are hinge-connected to each other at the height corresponding to the surface of water. When the floating structures on the surface of water have the rotations like pitch, roll and yaw by means of the external force like wind, the rotations are generated around one point on plane at which the floating structures and the surface of water meet each other.
At this time, a restoring force to an original state from an inclined state is a force applied to the rope, and according to moment characteristics, at this time, if the distance between the center of the rotation and the force applied to the rope becomes long and if the force applied to the rope becomes large, the restoration to the original state becomes fast. In case of the conventional floating photovoltaic systems as shown in FIGS. 1b and 1c, however, since the connection between the front row structures and the rear row structures is made at the height corresponding to the surface of water, the restoration moment is low so that the conventional floating photovoltaic systems are weak to the rotations of the structures.